coot vs crab louse

coot

noun
  • Body louse (Pediculus humanus). 

  • A success; something excellent. 

  • Any of various aquatic birds of the genus Fulica that are mainly black with a prominent frontal shield on the forehead. 

  • A foolish or eccentric fellow 

crab louse

noun
  • A parasitic insect, Pthirus pubis, that lives amongst the pubic hairs of humans and feeds on blood. 

How often have the words coot and crab louse occurred in a corpus of books? (source: Google Ngram Viewer )